In a multicore cable with a plurality of power line units each having a conductor to transmit power (hereinafter referred to as ‘core parts’), the core parts are arranged to be almost symmetric with respect to a center portion of the multicore cable and a protective layer is provided along outer surfaces of the core parts.
However, since the multicore cable includes the core parts, the roundness of the multicore cable may be difficult to maintain. In particular, when the multicore cable is installed or is wound about a turntable to install it under the sea, an external force such as lateral pressure may be applied thereto and thus the core parts included in the multicore part may be damaged. Thus, a filler is necessary to maintain the roundness of the multicore cable and protect the core parts included in the multicore part when the multicore cable is installed or when an external force such as lateral pressure is applied to the multicore part.
Recently, there is a growing need for an optical communication system based on an optical cable with optical fibers having high bandwidth characteristics than those of an existing copper communication line. Thus, generally, power cables for power transmission are manufactured in the form of a composite cable with optical units having optical fibers to simultaneously transmit power and information.
An optical cable with optical fibers is more advantageous than an existing copper line in terms of low loss characteristics, transmission characteristics such as a high bandwidth, etc., but has lower mechanical strength than a copper line and is thus a transmission medium having low mechanical reliability. Actually, a failure (disconnection, bending, or the like) may occur due to mechanical vulnerability of the optical fiber and various internal/external causes.
Accordingly, when the filler is provided, not only the above-described function but also a function of accommodating and protecting the optical unit are needed.